The present invention generally relates to applicators or fiberization dies for applying thermoplastic materials to a substrate or for producing nonwoven materials.
Thermoplastic materials, such as hot melt adhesive, are dispensed and used in a variety of situations including the manufacture of diapers, sanitary napkins, surgical drapes as well as many others. This technology has evolved from the application of linear beads or fibers of material and other spray patterns, to air-assisted applications, such as spiral and meltblown depositions of fibrous material.
Often, the applicators will include one or more dispensing modules for applying the intended deposition pattern. Many of these modules include valve components to operate in an on/off fashion. One example of a dispensing module is disclosed in U.S. Pat. No. 6,089,413, assigned to the assignee of the present invention, and the disclosure of which is hereby fully incorporated by reference herein. This module includes valve structure which changes the module between ON and OFF conditions relative to the dispensed material. In the OFF condition, the module enters a recirculating mode. In the recirculating mode, the module redirects the pressurized material from the liquid material inlet of the module to a recirculation outlet which, for example, leads back into a supply manifold and prevents the material from stagnating. Many other modules or valves have also been used to provide selective metering and/or on/off control of material deposition.
Various dies or applicators have also been developed to provide the user with some flexibility in dispensing material from a series of modules. For short lengths, only a few dispensing modules are mounted to an integral manifold block. Longer applicators may be assembled by adding additional modules to the manifold. Additional flexibility may be provided by using different die tips or nozzles on the modules to permit a variety of deposition patterns across the applicator as well. The most common types of air-assisted dies or nozzles include meltblowing dies, spiral nozzles, and spray nozzles. Pressurized air used to either draw down or attenuate the fiber diameter in a meltblowing application, or to produce a particular deposition pattern, is referred to as process air. When using hot melt adhesives, or other heated thermoplastic materials, the process air is typically also heated so that the process air does not substantially cool the thermoplastic material prior to deposition of the material on the substrate or carrier. Therefore, the manifold or manifolds used in the past to direct both thermoplastic material and process air to the module include heating devices for bringing both the thermoplastic material and process air to an appropriate application temperature.
In the above-incorporated patent applications, various embodiments of modular applicators are disclosed which allow a user to more easily configure the applicator according to their needs. Generally, these applicators include a plurality of manifold segments disposed in side-by-side relation, with each manifold segment including a dispensing module or valve and a positive displacement pump. Material, such as hot melt adhesive, flows through the side-by-side manifold segments to each pump. The pumps individually direct the material to each corresponding dispensing module. Heated process air is also directed through each manifold segment to the die tip or nozzle of the module and impacts the dispensed material to achieve a desired effect on the deposition pattern. A separate recirculating module is provided so that the material discharged from the pump flows to the recirculation module if the fiberization die module is shut off or closed. The recirculated flow ensures that flow through the pump is uninterrupted. These related applications disclose applicators having a single integral drive shaft extending through side-by-side positive displacement gear pumps or, alternatively, a segmented drive shaft which allows the manifold segments to be removed or added without the need for disassembling the entire manifold. In each case, the number of manifold segments and modules define the effective dispensing length of the applicator.
Despite the various progress made in the technology, there is still a need to increase the speed and efficiency at which an applicator may be configured and maintained or repaired. There is also a continuing desire to reduce the cost and complexity associated with these applicators.
The present invention generally provides a modular applicator for dispensing liquid including a plurality of manifold segments coupled in side-by-side relation. Each manifold segment includes a liquid supply passage and a liquid discharge passage. A plurality of pumps are respectively mounted in a removable manner to the plurality of manifold segments. Each of the pumps includes an inlet communicating with the liquid supply passage of the corresponding manifold segment, an outlet communicating with the liquid discharge passage of the corresponding manifold segment and a pumping mechanism for pumping the liquid from the inlet to the outlet. A drive motor is coupled to each of the pumps for operating each of the associated pumping mechanisms.
More specifically, the plurality of pumps are preferably gear pumps with one of the gears being a drive gear. A shaft is coupled between the drive motor and each of the drive gears to simultaneously operate each of the pumps. The system further includes a plurality of on/off dispensing modules respectively coupled with the manifold segments. These dispensing modules may be pneumatically operated valves and, for operational purposes, the manifold segments include air distribution passages for delivering pressurized control air to each of the pneumatically operated valves. An air control valve may be mounted to one or more of the manifold segments to selectively supply the pressurized control air to an associated one or more of the pneumatically operated valves. The manifold segments further include liquid distribution passages for delivering the liquid from one of the manifold segments to another of the manifold segments through opposed side surfaces thereof. Likewise, process air distribution passages also communicate between adjacent manifold segments for supplying heated process air to each of the modules. A pair of heating rods extend through each of the manifold segments for heating liquid and process air sections thereof. The liquid and process air sections of each manifold segment are thermally separated by one or more insulators, such as slots and/or bores.
The dispensing modules are preferably recirculating modules and appropriate passages are provided in each associated manifold segment to ensure that liquid is recirculated back into the manifold segment if the module is in an OFF position. The preferred liquid dispensing system also has the advantage that the pumps may be removed from the manifold segment without decoupling the manifold segments from one another. In this regard, the common drive shaft may be disengaged from one or more pumps by pulling the drive shaft out of one end of the manifold and, once disengaged, the appropriate pump or pumps may be removed and either repaired or replaced as necessary.
Various additional advantages and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description taken in conjunction with the accompanying drawings.